Re: [gentoo-dev] [RFC] Forced/automatic USE flag constraints (codename: ENFORCED_USE)

[Michał Górny]

On wto, 2017-06-06 at 19:39 +0200, Michał Górny wrote:
> On wto, 2017-06-06 at 14:08 +0200, Alexis Ballier wrote:
> > On Mon, 05 Jun 2017 20:10:12 +0200
> > Michał Górny <mgorny@g.o> wrote:
> > [...]
> > > > > Stand-alone makes little sense (and little trouble) but as you
> > > > > could have seen it's used nested in other thingies:
> > > > >
> > > > > 1. || ( ( a b ) ( c d ) e )
> > > > >
> > > > > 2. ?? ( ( a b ) ( c d ) e )
> > > > >
> > > > > 3. ^^ ( ( a b ) ( c d ) e )
> > > >
> > > > Yeah that's the nesting problem causing a parse error.
> > > > Those should be expanded to implications. What I'm relying onto is
> > > > all clauses to be of the form '[list of conditions]? [list of
> > > > constraints]'
> > >
> > > I've noticed that you turned the implications into multi-conditions,
> > > breaking all my scripts ;-). Is the [list of conditions] conjunctive
> > > or disjunctive?
> >
> > conjunctive as in foo? ( bar? ( baz ) ) -> [foo,bar]?[baz]
>
> Yeah, I guess that's useful. I didn't do that originally because I
> wanted the AST to be fully compatible with REQUIRED_USE in Gentoo. But I
> guess it doesn't hurt, and makes a lot of the code simpler.
>
> I've backported this change and adjusted all the remaining modules to
> work with it correctly.
>
> >
> > [...]
> > > > > The question is whether we want to:
> > > > >
> > > > > a. actually try to solve this nesting insanity,
> > > > >
> > > > > b. declare it unsupported and throw REQUIRED_USE mismatch on user,
> > > > >
> > > > > c. ban it altogether.
> > > >
> > > >
> > > > I don't think it is *that* insane to support nesting :)
> > > >
> > > > > ( ^^ ( ?? ( a b ) c ( d e ) ) f )
> >
> > If you really need that then you'd need to expand it manually. It seems
> > better to have it expanded internally automatically.
> > Remember you were the one wanting to keep || & co because they're
> > simpler to read and write ;)
> >
>
> Well, I was able to implement the logic for all-of blocks outside
> and inside other n-ary constraints, including the necessary logic
> transformations. Fun fact is, I was able to do it without implementing
> a complete set of logic functions and transformations in AST ;-).
>
> I've just made it fail (correctly this time) with any other kind of
> nesting -- I don't think it's going to have a real use case and even if
> it did, there are more readable ways of solving the same problem.
>
> The question is -- will you rebase now on top of my changes
> (and preferably use nice logical changes with good commit messages),
> or should I try later to merge the rest of your code in? ;-)
>

I've rebased your changes and pushed them. However, I didn't alter
replace_nary to include '!a...' since it made the results worse for
me... it's possible that I did it wrong.

There's also some issue with all-of expressions that exhibits itself
on ibus. I'll look at that later.

-- 
Best regards,
Michał Górny